[PATCH] tcp: Use BIT() for OPTION_* constants

[PATCH] tcp: Use BIT() for OPTION_* constants

[Leonard Crestez]

Extending these flags using the existing (1 << x) pattern triggers
complaints from checkpatch. Instead of ignoring checkpatch modify the
existing values to use BIT(x) style in a separate commit.

Signed-off-by: Leonard Crestez <cdleonard@gmail.com>

---
This was split away from a longer series implementing RFC5925
Authentication Option for TCP.

Link: https://lore.kernel.org/netdev/dc9dca0006fa1b586da44dcd54e29eb4300fe773.1635784253.git.cdleonard@gmail.com/

 net/ipv4/tcp_output.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 6867e5db3e35..96f16386f50e 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -406,17 +406,17 @@ static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
 static inline bool tcp_urg_mode(const struct tcp_sock *tp)
 {
 	return tp->snd_una != tp->snd_up;
 }
 
-#define OPTION_SACK_ADVERTISE	(1 << 0)
-#define OPTION_TS		(1 << 1)
-#define OPTION_MD5		(1 << 2)
-#define OPTION_WSCALE		(1 << 3)
-#define OPTION_FAST_OPEN_COOKIE	(1 << 8)
-#define OPTION_SMC		(1 << 9)
-#define OPTION_MPTCP		(1 << 10)
+#define OPTION_SACK_ADVERTISE	BIT(0)
+#define OPTION_TS		BIT(1)
+#define OPTION_MD5		BIT(2)
+#define OPTION_WSCALE		BIT(3)
+#define OPTION_FAST_OPEN_COOKIE	BIT(8)
+#define OPTION_SMC		BIT(9)
+#define OPTION_MPTCP		BIT(10)
 
 static void smc_options_write(__be32 *ptr, u16 *options)
 {
 #if IS_ENABLED(CONFIG_SMC)
 	if (static_branch_unlikely(&tcp_have_smc)) {

base-commit: d4a07dc5ac34528f292a4f328cf3c65aba312e1b
-- 
2.25.1

Re: [PATCH] tcp: Use BIT() for OPTION_* constants

[Eric Dumazet]

On 11/3/21 3:17 PM, Leonard Crestez wrote:
> Extending these flags using the existing (1 << x) pattern triggers
> complaints from checkpatch. Instead of ignoring checkpatch modify the
> existing values to use BIT(x) style in a separate commit.
> 
> Signed-off-by: Leonard Crestez <cdleonard@gmail.com>
>

Yes, I guess checkpatch does not know that we currently use at most 16 bits :)

u16 options = opts->options;

Anyway, this seems fine.

Reviewed-by: Eric Dumazet <edumazet@google.com>

RE: [PATCH] tcp: Use BIT() for OPTION_* constants

[David Laight]

From: Eric Dumazet
> Sent: 03 November 2021 22:50
> 
> On 11/3/21 3:17 PM, Leonard Crestez wrote:
> > Extending these flags using the existing (1 << x) pattern triggers
> > complaints from checkpatch. Instead of ignoring checkpatch modify the
> > existing values to use BIT(x) style in a separate commit.
> >
> > Signed-off-by: Leonard Crestez <cdleonard@gmail.com>
> >
> 
> Yes, I guess checkpatch does not know that we currently use at most 16 bits :)
> 
> u16 options = opts->options;
> 
> Anyway, this seems fine.

Doesn't BIT() have a nasty habit of generating 64bit constants
that just cause a different set of issues when inverted?
It may be safe here - but who knows.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH] tcp: Use BIT() for OPTION_* constants

[Eric Dumazet]

On 11/4/21 2:17 AM, David Laight wrote:
> From: Eric Dumazet
>> Sent: 03 November 2021 22:50
>>
>> On 11/3/21 3:17 PM, Leonard Crestez wrote:
>>> Extending these flags using the existing (1 << x) pattern triggers
>>> complaints from checkpatch. Instead of ignoring checkpatch modify the
>>> existing values to use BIT(x) style in a separate commit.
>>>
>>> Signed-off-by: Leonard Crestez <cdleonard@gmail.com>
>>>
>>
>> Yes, I guess checkpatch does not know that we currently use at most 16 bits :)
>>
>> u16 options = opts->options;
>>
>> Anyway, this seems fine.
> 
> Doesn't BIT() have a nasty habit of generating 64bit constants
> that just cause a different set of issues when inverted?
> It may be safe here - but who knows.

BIT() does not use/force 64bit constants, plain "unsigned long" ones.

Really this patch looks a nop to me.